1. Field of the Invention
This invention relates to a chip, more particularly to a chip having a light trapping region and a light reflective region for position-alignment.
2. Description of the Related Art
A chip, which is made using processes for forming semiconductor integrated circuits, has a position-alignment region for subsequent processes, such that a poor yield rate due to misalignment can be prevented.
Referring to FIGS. 1 and 2, a conventional chip 1 includes a chip body 11, a metal layer 12 formed on the chip body 11, and a protective layer 13 formed on the metal layer 12.
The chip body 11 includes a plurality of predetermined metal interconnect circuits and integrated electrical elements. Since the structures of the circuits and electrical elements are well-known in the art, detailed descriptions thereof are omitted herein for the sake of brevity.
The metal layer 12 includes a metal interconnect region 121 and a position-alignment region 122. The metal interconnect region 121 cooperates with the chip body 11 to form a complete interconnect structure. After the subsequent packaging and wire-bonding processes, the operation of the chip 1 can be controlled by an external circuit. The position-alignment region 122 is a complete metal area and cooperates with the protective layer 13 to form a position-alignment pattern.
The protective layer 13 is patterned to have a through hole 131 to partially expose the position-alignment region 122. In detail, the protective layer 13 is formed over the metal layer 12 to have a predetermined thickness, and then, the through hole 131 is formed in a position corresponding to the position-alignment region 122 by a lithography process using a mask. Because the protective layer 13 and the position-alignment region 122 exposed from the protective layer 13 have different light reflection rates, brightness contrast is formed between the protective layer 13 and the position-alignment region 122 when light is irradiated thereto.
It should be noted that in order to form the brightness contrast for position alignment, the processes for forming and patterning the protective layer 13 are further required after the metal layer 12 is completely formed. Accordingly, the cost for forming the conventional chip is relatively high.
Besides, the protective layer 13 is made of titanium nitride (TiN), and the metal layer 12 is made of copper, aluminum, etc. The brightness contrast ratio between the protective layer 13 and the metal layer 12 is about 45 (see FIG. 9). Although the brightness contrast ratio of 45 is sufficient for position alignment, it is still low and further improvement is needed.